Manufacture of wire-drawing dies



July 12 1927 K, B. LEWIS ETH MANUFAC'TURE oF WIRE DRAW-'ilus DIES FiledMarcnm, 19224"l Patented July l2, 1927.

UNITED STATES PATENTOFFICE. i

KENNETH B. `LEWIS AND1 FRANK H. ELLSWORTH, `0F WORCESTER, MASSACHUSETTS,

ASSIGNORS TO MORGAN CONSTRUCTION COMPANY, OF WORCESTER, MASSACHU- SETTS,A CORPORATION 0F MASSACHUSETTS. e

murnc'runn or WIRE-nnAWING mns.

Application inea marcan, 1924,` serial No. 699,263.

Our invention relates tothe manufacture of wire drawingdies and has forits ob'ect to provide an improved methodl of pro ucing dies capable o'laccurately finishing more wire than diesz heretofore Adem lcyed ,forl,the same purpose. A further obgect of ourinvention is to provide animproved method, by the `practice ,of which. larfge numbers' of dies can`be produced which willbe nabsolutely uniform Cas regards thejsize 1an-dshape of the orifice through which "the metal drawn and all of whichdies will have the same degree of hardness. Astillfurtheryobject is toprovide anviinproved method car pable of being carried on byvcomparativ'ely l unskilled operators with a consequentv saving inmanufacturing costs, as willA hereinafter appear.'

In the manufacture of the wire drawing dies, the formation of theorifice, or hole, through .which the metal is drawn, is of theutmostimportance, and Ythe accuracy of the die and the amount of metalwhich V.may be drawn therethrough is very largely' deter# mined bv themanner of forming` the hole. Therefore, in order that the nature andscope of rour invention may be fully understoodthere follows a briefdiscussion of the methods heretofore commonly employed in themanufacture of wire drawing dies. In the production of dies Vcomposeilvof chilled cast iron,the holes are reamed to exact size by skilledoperators, the real nin of the holes involving the `actual removal o'metal from the die. It is usually ssible to draw only one bundle ofwire: rough the hole of a cast iron die, after whichthe hole must berearned out again' to `a larger size by a skilled operator, thisprocedure being followed after each draft 'until the hole becomes toolarge for the strength of the die and the die is scrap ed. 1

In the production of stee dies to be used for drawing Ordinar sizes ofwire, agrade of steel is employe whichv will harden if heated andquenched. The usual practice when `producing steel dies is to keep themetal in an annealed state, 'hardening the metal only in the immediatevicinity of the hole by coldworking. V`When it is desired to reform aworn holeV ina steel die, the worn-out hole is partially closed by handhammering the metal around thesame.

the operator.

hammering hardens vthe metal and at the same time crowds the` metal intother-hole so that, after hammering, thehole is smaller. f

The hammered hole is then enlarged to its original size by careful handpunching,y

which shapes and sizes the hole and further hardens the metal. Therestoring. of a hole to size requires considerable skill and experienceon the lpart of the operator, for f the hammering must neither betoojheavy nor too light, and the blows must be evenly spaced around thehole 'and not too close to it. The tool with which, the hole is punchedto its final size is tapered, sothat'the size of the hole depends'uponthe `depth to which the punch is driven."` Therefore,` great skill mustbe .exercized by the yoperator when punch-ing the hole, and the sizeofthe hole "must be tested after each blow on Vthe punch.

The operation of` resetting holes in steel dies of thisy 'character' isyobviously slow and costly, the, success of the operationv dependinglargely on the vskill and Vexperience of It is usuallypossible toaccurately draw but one bundle through a reset hole of a' soft steeldie.

In the ,drawing of large sizes of` wire, w'hi'ch are to have onlyaslight'red'uction,

steel. dies haveheretofore been employed to a limited extent which havebeen hardened by heating and quenching. In the. production of such dies,a stream ofwater isrpasse'd through the orifice while the 4metal is redhot and in the resulting shrinkage'of the 'imetah theopeningbecomes'snialfler than its `original size. The opening is then restoredtoits original size by lapping, that is, by the use ofa suitable'rotating toolcarrying "an abrasive which removes the scale and bringsthe hole to true roundne'ss. Hardenedl and lapped steel diesrequirefmuch skillin their preparation, and both `the Adies and `theholes must be so shaped as to secure uniform'shrinkage.

` From a consideration of the above, it is 'apparent that inl all casesthe working, or

resizing, ofthe holes requires skilled operators,y and 4that it isalways diicult to obtain absolute uniformity' in the sizes of holes owin"to the fact that practically all the work is.4 oneby hand.Furthermore,an entire mill employing perhaps two hundred or .threehundredimn, may *be ythrown out' qof employness of the metal.

ment temporarily by the absence from work of two or three skilled dieworkers.

As previously pointed out, it is the object of our invention to providean improved method of producing dies capable of accurately tinishingmore wire than either cast- .iron or soft steel dies as previously made,the practice of our invention permitting the production oit' largenumbers of dies absolutely uniform as regards the size and shape of theopening and the degree of hard- The production of dies by the practiceof our invention is in no way dependent upon the manual skill ofoperators, the uniformity and (piality of the product being assured bymechanical means, will hereinafter more fully appear, reference beinghad to the accompanying drawings in which i Fig. 1 is a sectional viewof a die at the time of carrying out the first' step of our method.

Fig. 2 is a diagrammatic view illustrat- `ingmeans for carrying ont thesecond step of our method.

- Fig. 3 is a sectional view similar to Fig. 1, showing the ap earanceof the die after the performance o the second ste Fig. 4 is adiagrammatic view i lustrating means for carrying out the third step ofour method.

Fig. 5 is a view of the punch used in Fig. 4. l

Fig. 6 is a view'similar to Flg. 1, illustrating the appearance of thedie after the performance of the third step of our method.

Like reference characters refer to like -parts in the different figures.

'Referring' to theV drawings, Fig. 1 illustrates a usual formof die 1preferably composedv of a high grade of steel. The die is provided witha hole 2 originally formed, roughly, in any desired manner, at the timeof making the die, and our invention has to do with the setting orresetting of this hole 2, preparatory to drawing wire therethrough.rl`he hole 2 flares outwardly on one side of the die to guide the wireto the reduced cylindrical portion 2 of the hole which determines thesize of the wire drawn therethrough in the direction of the arrow Indrawing wire through the cylindrical or reducing portion 2a, it has beenfound that the metal of the die is worn away, as indicated in dottedlines at o, a, in Fig. 1, thus forming' an annular pocket surroundingthe entrance to the reducing portion 2a. The formation of this pocketsoon destroys the accuracy-of the die which must then be reset. At thispoint itshould be borne in mind that in the practice of our invention,it is immaterial whether the hole 2, shown in Fig. 1, is that of a newdie which is to be set for theifirst time, -or whether it is the wornhole of an old die which is to be reset.

,In carrying out our invention the die 1 is placed in azsuitable heatingfurnace in which it is heated to a temperature well above its criticalpoint. The furnace employed for heating the die is preferably of thetype in which the degree of heating of the material therein may becontrolled so that when a number of dies are successively placedinthefurnace, all o-l" them will be brought to substaijitially the sametemperature. f

rllhe die having been heated to the desired degree, it is withdrawn fromthe furnace Yand immediately placed on the bed if) of a hammeringmachine, diagrammatically illnstrated inv Fig. 2. lThe hann'neringmachine isof the automatic type in which the hammering element 4t alwaysoperates in a uniform manner and is always adapted to strike an objectplaced. on its bed 3y at the same rate and with the same force for a.given setting of the machine. An automatic hammering machine of thistype is fully vshownand described in U. S. Patent No. 1,310,968,issuedJuly 22, 1919, to Connor and Slinger, and it is not believednecessary to burden the present application with a detailed descriptionthereof.

Suffice to say that when the machine shown in Fig. 2 is set inoperation, the hammering element 4 is adapted to strike the 'face 1a ofthe die 1 a series of blows distributed around the opening 2, the blowsbeing delivered in a generally spiral path automatically determined byrotative movement of the bed 3 and simultaneous movement of the`elem-ent 4 withV respect to the axis of the die hole 2. For a givensetting of the machine7 the haminering. of each die placed on the bed 3is exactly the same and is carried on independently of the operator ofthe machine.

The above described han'n'nering of the die 1 in its heated conditioncauses the metal therein to be somewhat condensed. around the opening 2so that the cylindrical portion 2 is, after hammering. slightly sniallerthan this portion was before being heated. The contraction of theopeningl 2 is shown on a somewhat exaggerated scale in Fig. 3. fromwhich it is apparent that the pocket (L shown in Fig. 1 has disappeared,and that an annular shoulder has taken its place.

'lne'han'lmered die l is then immediately placed, While still hot, onthe bed 5 ot a power punch. which is illustrated diagral'nmatically inFig.- t. vThe punching tool (i of this machine is the exact size andshape of the desired die opening and the machine is of such a type thatupon release of its clutch, or other controlling device, the punchingtoolG is adapted to `make one stroke in the die 1.to a predetermineddepth. The tool 6 is shown in Fig. 5, from which it is apparent that theworking stroke of the tool 6 lill 1n the heated die 1 shapes thelhole2`to the 'i Lllvihilewe'. are aware that the hammering exact sizeand .shape as shown in Fig.

The punched die 1 is then moved' from the punching machine, whilestillin a heated condition, and is dropped into an oil bath which serves toharden the metal by quenching. I y

The above described operations are adapted to be carried out in rapidsuccession, and each die that is handled in accordance with our methodis treated in exactly the same manner. lVhen a number of dies are beinghandled, they are all brought to the same temperature by the continuousheating furnace, after which the automatic hammering machine operatesupon each of thev dies in the same manner, the amount of hammering whicheach die undergoes notbeing susceptible of control by the operator. Thedies are then all operated upon by the punching machine in exactly thesame manner, the punch 6 always descending to the same point withrelation to the bed 5, and with relation to the die face, so that theholes 2 produced in successive dies are identical in size and shape. Byreason of the fact that each die is operated upon in exactly the samemanner, the dies reach the oil at a uniform temperature and areconsequently hardened to exactiy the same degree. v i v Te have foundthat dies producedby the practice of our invention being exactlyuniform, as regards the size of the o enings and degree of hardness, arealso uni orm in their behavior when used to draw wire, that is to say,a. number of dios formed in accordance with our invention are adapted topro- `duce wire of uniform size, and we have found that such dies willsatisfactorily finish about six times as much wire Vas cast iron, orsoft steel dies, used for the same purpose. y u

Furthermore, the production of dies in accordance with our invention canbe carried on with much less labor and expense than has heretofore beennecessary for` setting of cast iron or steel dies. Obviously theheating, hammering, punching, and quenching of dies in accordance withour method can be carried on by comparatively unskilled operators,inasmuch as the hammering and punching machines are entirely7 automaticin their operation, while the degree of heating and cooling of the diesis determined entirely by the control of the heating furnace and thelength of time it takes a die to be operated upon by the hammering andpunching machines. The fact that the dies require no handling, otherthanthe mere transfer from one machine to another, results in dies being setat a much faster rate by the practice of our invention than is possiblewhen the setting is performed by the manual labor of skilled operators,as previously described.

and punching of `dies hasv beenheretofore carried y,en byhand, webelieve that the automatic hammering ofy ydiesfollowed by hot vvowel'Cpimchi'ng as a. means of producing al nislie hole, "is enti-rely new.We have in carrying out? our invention that 'thequenchingofthe"diesffafter hot punching results in the production of a finishedhole which it is not necessary to lap out in order to polish the holeand free it from scale. This production of a finished hole by asingleoperation is doubtless due to the fact that the punch whichentersand iinishes the V hole in the hot die leaves a filmof oil whichburns and protects the sides 'of vthe hole against oxidation until it isquenched.

We claim, Y y' 1. The improvement in the art of manufacturing wiredrawing dies, which consists in heating dies to a uniformvdegree,automatically hammerlng the heated dies a uniform amount, powerpunchingfthe heated.

dies in the same manner, and quenching the punched dies to obtain auniform degree of hardness.

2. The iniprovcment in the art of manufacturing wire drawing dies whichconsists in power punching a heated die by a single quick stroke toproduce a finished hole therein, the punching being immediately followedby quenching to harden the die.

3. An improved method of making wire drawing dies,v which consists infirst heating a die a predetermined amount, then automatically hammeringsaid die, then power punching said die by a single quick stroke toproduce a finished hole, and finally in hardening said die by quenching.y

4.v An improved method of making wire drawing dies, which consists inlirst heating a die to a predeterminedl degree, then automaticallyhammeringsaid die a predeter-V mined amount, then power punching saiddie by a single quick stroke to produce a finished hole of apredetermined size, and then hardening said die by quenching.

5. An improved method of making wire drawing dies, which consists infirst heating a die to a point above its critical temperature, thenautomatically hammering said die out of its original form, then powerpunching said die by a single quick stroke to produce a finished hole ofpredetermined size, and finally `in hardening said die by quenching.

6. An improved method of making `wire drawing dies, which consists iniirst heating a die to a predetermined temperature, then subjecting saiddie to the action of an automatic hammering machine which alters theshape of the die orice a predetermined `degree, then subjecting said dieto a single quick stroke of a power punch with a tool of predeterminedshape and size,` which penetrates said die to a predetermined depth, endfinally in hardening said die by quenching.

7 An improved method of making Wire drawing dies, which consists inheating a number of dies to the same degree, then hammering each of saiddies a predetermined amount, then power punching each of seid dies by eysingle quick stroke to the same size and depth, and finally in uniformly10 hardeningeach of said dies by quenching at the same temperature.

Dated this third day of March, 1924.

KENNETH B. LEWIS. FRANK H. ELLSWORTH.

